string types: const(char)[] and cstring

[Daniel Keep]

Walter Bright wrote:
> Under the new const/invariant/final regime, what are strings going to be
> ? Experience with other languages suggest that strings should be
> immutable. To express an array of const chars, one would write:
> 
>     const(char)[]
> 
> but while that's clear, it doesn't just flow off the keyboard. Strings
> are so common this needs an alias, so:
> 
>     alias const(char)[] cstring;
> 
> Why cstring? Because 'string' appears as both a module name and a common
> variable name. cstring also implies wstring for wchar strings, and
> dstring for dchars.
> 
> String literals, on the other hand, will be invariant (which means they
> can be stuffed into read-only memory). So,
>     typeof("abc")
> will be:
>     invariant(char)[3]
> 
> Invariants can be implicitly cast to const.
> 
> In my playing around with source code, using cstring's seems to work out
> rather nicely.
> 
> So, why not alias cstring to invariant(char)[] ? That way strings really
> would be immutable. The reason is that mutables cannot be implicitly
> cast to invariant, meaning that there'd be a lot of casts in the code.
> Casts are a sledgehammer, and a coding style that requires too many
> casts is a bad coding style.

Thanks for the update; I'm happy to have const strings, and use char[]
manually when I want to mutate something.

One question though: are the parens necessary?  I was under the
impression that const and invariant applied to reference types, so it
would be const char[] or const(char[]), since char by itself is just a
value type.

...this is going to turn into one of those mega threads where we all run
around in circles trying to work out which one is which, isn't it?

	-- Daniel

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